Inkjet recording ink for sublimation transfer and method of dyeing

ABSTRACT

An ink for sublimation transfer ink jet recording includes water, at least one sugar alcohol containing not less than four OH groups, a sublimation dye, a dispersant, and a compound expressed by the following chemical formula (I):
 
R—O—(CH 2 CH 2 O) n —H  (I)
where R is an alkyl group having a carbon number of 25 to 150 and n is from 2 to 100. The ink is printed on a sheet medium by ink jet printing, and then the sheet medium is heated to sublimate and transfer the sublimation dye onto an object to be dyed. The ink for ink jet recording and the sublimation transfer dyeing method using the ink not only can maintain performances such as storage stability and high-quality recording images, but also can reduce environmental pollution, effectively prevent nozzle clogging, exhibit good dispersion stability, and achieve a high redispersion property that ensures stable ejection both during long continuous operation and after stopping the operation for a long time.

TECHNICAL FIELD

The present invention relates to ink for sublimation transfer ink jetrecording in an ink jet recording system and a sublimation transferdyeing method using the ink. Specifically, the present invention relatesto ink for sublimation transfer ink jet recording that includes asublimation dye used in a piezo ink jet system and can reduceenvironmental pollution, effectively prevent nozzle clogging of arecording head, and have excellent storage stability, and a sublimationtransfer dyeing method.

BACKGROUND ART

Water-based ink for ink jet recording is used generally in the form of awater-soluble dye solution or a liquid obtained by dispersing awater-insoluble color material into water or an aqueous solutionincluding a water-soluble organic solvent. On the other hand, ink forink jet recording that includes a sublimation dye has been used forsublimation transfer dyeing. For example, there is a method in which theink including a sublimation dye is printed by ink jet printing on asheet medium such as paper, and this medium is then put on a hydrophobicfiber product or resin film product for sublimation transfer. There isalso another method, as disclosed, e.g., by JP 2002-79751 A, in whichthe ink including a sublimation dye is printed by ink jet printing on afilm product that has a releasable ink receptor layer and can be usedfor sublimation and diffusion dyeing, the film product is then heated sothat the lower layer is dyed by sublimation and diffusion, and the inkreceptor layer is removed.

The sublimation dye ink is used generally in the form of a liquidobtained by dispersing the sublimation dye into an aqueous solutionincluding water, a water-soluble organic solvent, and a dispersant.However, the water-soluble organic solvent is evaporated with water byheat treatment, e.g., when the ink is printed on the paper medium by inkjet printing, the medium is then put on a transfer object, and theobject is dyed by sublimation transfer while heating, or when the ink isprinted on the releasable ink receptor layer of the film product thatcan be used for sublimation and diffusion dyeing, the film product isthen heated to sublimate and diffuse the sublimation dye so that thelower layer of the film product is dyed. This is the point differentfrom ink jet printing that is used only for general printing purposes.The sublimation transfer dyeing method requires heating for apredetermined time at temperatures higher than the sublimation point ofthe sublimation dye. Therefore, even a high-boiling organic solvent maybe evaporated. Particularly for a high-boiling organic solvent such asglycerin, the temperature is reduced to a condensation point shortlyafter the evaporated solvent is released into the atmosphere, thuscausing smoky steam. This is considered to be undesirable because theappearance becomes extremely worse. One possibility for avoiding such aproblem is to use a low-boiling solvent that does not cause any smokysteam. However, the low-boiling solvent is the same as the high-boilingorganic solvent in release of the evaporated solvent into theatmosphere. In either case, therefore, environmental pollution (e.g.,working environment) is a problem.

Characteristics required for ink for ink jet recording are as follows:(1) ejection stability while preventing nozzle clogging; (2) storagestability; (3) high-quality recording images resulting from uniformityin the direction of ink ejected, the ejection amount, and the dot shape;(4) quick drying and fixation; and (5) high print density.

In an ink jet recording system, ink should be ejected from thin nozzlesas ink droplets. Therefore, (1) is particularly important. When the inkjet recording system is of the drop-on-demand type, the ejection of inkfrom the nozzles is stopped temporarily even during continuousoperation. This may lead to an ejection failure in long continuousoperation.

Unlike a water-soluble dye, the ink for sublimation transfer ink jetrecording that includes a sublimation dye tends to cause clogging, e.g.,because precipitates (aggregates) are generated by the degradation ofdispersion stability and moisture is evaporated from the nozzles. Inparticular, when the apparatus is not operated for a long time, cloggingis likely to occur due to evaporation of moisture.

Therefore, a humectant is added to suppress the evaporation of moisture.Examples of the humectant include a high-boiling organic solvent ofglycols such as glycerin or polyethylene glycol, and saccharides.

As described above, however, the sublimation transfer method requiresheating for a predetermined time at temperatures higher than thesublimation point of the sublimation dye. Therefore, even if ahigh-boiling organic solvent is used as a humectant, the solvent isevaporated at a heating temperature during sublimation transfer,resulting in environmental pollution. Thus, it is necessary to use ahumectant that is not an organic solvent, is not evaporated by heatingin sublimation transfer, and has no adverse effect on thecharacteristics (1) to (5) required for the ink.

As an example of a humectant other than a water-soluble organic solvent,JP 57(1982)-57762 A discloses a water-based inkjet ink including awater-soluble dye and sorbitol. JP 60(1985)-72968 A and JP 62(1987)-101672 A disclose a water-based pigment ink including pigment andsorbitol. JP 2(1990)-214785 A discloses a water-based ink for ball pointpen that includes maltitol and uses a water-soluble dye or pigment as acolorant. JP 2001-115070 A discloses that xylitol and a water-solubleorganic solvent are used for carbon black dispersions.

In the above conventional techniques, sugar alcohol has been used as ahumectant for a pigment ink or water-soluble dye ink. However, none ofthe conventional techniques disclose whether sugar alcohol can be usedas a humectant for an ink in which a sublimation dye is dispersed with adispersant. Moreover, no study has been conducted on a sublimation dyeink that includes the smallest possible amount of water-soluble organicsolvent in consideration of environment, and no technique has sought tofind a solution to a problem that may arise with that case. Further,sugar alcohol should be used as a humectant while taking into accountthe fact that it has no adverse effect (e.g., oxidation-reduction) onthe sublimation dye.

JP 2000-265098 A discloses an inkjet ink that includes water, acolorant, and a compound expressed by the following chemical formula(II):R-A-(CH₂CH₂O)_(x)—H  (II)where R is linear saturated hydrocarbon having a carbon number of 14 to23, A is O or OCO, and x is an integer of 1 to 3. This ink may include ahumectant as needed.

However, JP 2000-265098 A discloses “various dyes, pigment, or coloredpolymer/wax can be used as a colorant, and a water-soluble dye isparticularly preferred. Any type of water-soluble dye, e.g., . . . canbe used, and an acid dye and direct dye are particularly preferred.” Inthis document, only acid dye is used actually in the example. Therefore,as is evident from the description, JP 2000-265098 A does not disclosethe use of the compound expressed by the chemical formula (II) in asublimation dye ink. Even if R is polyoxyethylene higher alkyl ethershaving a carbon number of not more than 23, it is not possible toprovide an ink composition with a high redispersion property when asublimation dye is used as a colorant.

To solve the above problems of a conventional ink for ink jet recordingthat includes a sublimation dye, an object of the present invention isto provide an ink for ink jet recording that not only can reduceenvironmental pollution and maintain required performances such asstorage stability and high-quality recording images, but also caneffectively prevent nozzle clogging, exhibit good dispersion stability,and achieve a high redispersion property that ensures stable ejectionboth during long continuous operation and after stopping the operationof an apparatus for a long time. Another object of the present inventionis to provide a sublimation transfer dyeing method using this ink.

SUMMARY OF INVENTION

An ink for sublimation transfer ink jet recording of the presentinvention includes water, at least one sugar alcohol containing not lessthan four OH groups, a sublimation dye, a dispersant, and a compoundexpressed by the following chemical formula (I):R—O—(CH₂CH₂O)_(n)—H  (I)where R is an alkyl group having a carbon number of 25 to 150 and n isfrom 2 to 100.

A sublimation transfer dyeing method of the present invention includesprinting the ink for sublimation transfer ink jet recording on a sheetmedium by ink jet printing, and heating the sheet medium to sublimateand transfer the sublimation dye onto an object to be dyed.

DETAILED DESCRIPTION OF INVENTION

An ink for ink jet recording of the present invention that uses asublimation dye as a color component is excellent not only inmaintaining required performances such as storage stability andhigh-quality recording images, but also in achieving a high redispersionproperty with reduced environmental pollution, effectively preventingnozzle clogging, and ensuring stable ejection by normal cleaning bothduring long continuous operation and after stopping the operation of anapparatus for a long time.

A sublimation transfer dyeing method of the present invention allows theink for sublimation transfer ink jet recording to be printed by ink jetprinting, followed by sublimation transfer. Thus, this method can reduceenvironmental pollution while maintaining required performances such asstorage stability and high-quality recording images of the ink used fordyeing. Therefore, the ink used can improve the redispersion propertyand effectively prevent nozzle clogging, which makes it possible toperform dyeing all the time and to ensure stable ejection by normalcleaning both during long continuous operation and after stopping theoperation of an apparatus for a long time.

In the ink for sublimation transfer ink jet recording and thesublimation transfer dyeing method using the ink of the presentinvention, it is preferable that the sugar alcohol containing not lessthan four OH groups is at least one selected from the group consistingof D-sorbitol, xylitol, and maltitol.

In the ink for sublimation transfer ink jet recording and thesublimation transfer dyeing method using the ink of the presentinvention, it is preferable that R is an alkyl group having a carbonnumber of 30 to 50 and n is from 10 to 50 in the chemical formula (I).

In the ink for sublimation transfer ink jet recording and thesublimation transfer dyeing method using the ink of the presentinvention, it is preferable that hydrophile-lipophile balance (HLB) ofthe compound expressed by the chemical formula (I) is not less than 10.

In the ink for sublimation transfer ink jet recording and thesublimation transfer dyeing method using the ink of the presentinvention, it is preferable that the sublimation dye is at least oneselected from the group consisting of a disperse dye and a solvent dye.

In the ink for sublimation transfer ink jet recording and thesublimation transfer dyeing method using the ink of the presentinvention, it is preferable that the dispersant is at least one selectedfrom the group consisting of an anionic surfactant, a nonionicsurfactant, and a high-molecular surfactant.

In the ink for sublimation transfer ink jet recording and thesublimation transfer dyeing method using the ink of the presentinvention, it is preferable that the amount of the sugar alcoholcontaining not less than four OH groups is 0.5 to 50 wt % with respectto the total weight of ink.

In the ink for sublimation transfer ink jet recording and thesublimation transfer dyeing method using the ink of the presentinvention, it is preferable that the amount of the sugar alcoholcontaining not less than four OH groups is 0.5 to 50 wt %, the amount ofthe sublimation dye is 0.2 to 12 wt %, the amount of the dispersant is0.1 to 20 wt %, and the amount of the compound expressed by the chemicalformula (I) is 0.1 to 8 wt % with respect to the total weight of ink.

In the ink for sublimation transfer ink jet recording and thesublimation transfer dyeing method using the ink of the presentinvention, it is preferable that the ink does not substantially includea water-soluble organic solvent (i.e., the substantial amount of thewater-soluble organic solvent is 0 wt %).

According to the present invention, the sublimation dye is dispersedusing the dispersant, and the sugar alcohol containing not less thanfour OH groups is included as a humectant in the ink having the chemicalformula (I), thereby making the amount of water-soluble organic solventas small as possible to achieve an environmentally oriented sublimationdye ink.

Unlike polyoxyethylene higher alkyl ethers used in a conventional inkfor ink jet recording, the compound expressed by the chemical formula(I) of the present invention includes an alkyl group having a carbonnumber of not less than 25. The upper limit of the carbon number of thealkyl group generally is not more than 150. As a conventional example,natural or synthetic alcohol compounds have been commercially available.However, these compounds normally include an alkyl group having a carbonnumber of about 12 to 18. The above-described JP 2000-265098 A disclosesa polyoxyethylene alkyl ether compound that includes an alkyl grouphaving a carbon number of 14 to 23.

However, when a sublimation dye is used as a colorant, it is notpossible to achieve an ink composition with a high redispersion propertyeven by using the polyoxyethylene higher alkyl ethers having a carbonnumber of less than 25. Therefore, the present invention requires that Rshould be an alkyl group having a carbon number of 25 to 150.

The sugar alcohol used in the present invention is preferably sugaralcohol derived from monosaccharide or sugar alcohol derived fromdisaccharide. Examples of the sugar alcohol derived from monosaccharideinclude threitol, erythritol, arabitol, ribitol, xylitol, lyxitol,sorbitol, mannitol, iditol, gulitol, talitol, galactitol, allitol, andaltritol. Examples of the sugar alcohol derived from disaccharideinclude maltitol, isomaltitol, lactitol, and turanitol. The presentinvention requires sugar alcohol containing not less than four OHgroups. The sugar alcohol containing less than four OH groups, e.g.,glycerin is not preferable because it is evaporated by heating insublimation transfer. Among the above examples, D-sorbitol, xylitol, andmaltitol are preferred, and D-sorbitol is particularly preferred in viewof solubility and cost efficiency. They can be used individually or as amixture of two or more types of sugar alcohol. To adjust the inkviscosity and to prevent clogging by utilizing a moisture retentioneffect, the amount of sugar alcohol used in the present invention ispreferably 0.5 to 50 wt %, more preferably 2 to 40 wt %, and even morepreferably 5 to 25 wt % with respect to the total weight of ink.

It is preferable that that a water-soluble organic solvent is not used(i.e., the substantial amount of water-soluble organic solvent is 0 wt%) in the present invention. However, the water-soluble organic solventmay be used together with the sugar alcohol, as long as it does notimpede the purpose of the present invention. Examples of thewater-soluble organic solvent include polyhydric alcohols such asethylene glycol, diethylene glycol, propylene glycol, butylene glycol,triethylene glycol, tetraethylene glycol, polyethylene glycol,polypropylene glycol, thiodiglycol, and glycerin, glycol ethers such asethylene glycol monomethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diethylene glycol monobutyl ether,and propylene glycol monomethyl ether, alcohols such as isopropylalcohol, methanol, and ethanol, and basic solvents such asN-methyl-2-pyrrolidone and triethanolamine.

Among these water-soluble organic solvents, glycerin, diethylene glycol,polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol400, and propylene glycol are preferred in view of moisture retention.

They can be used individually or as a mixture of two or more solvents.

In a compound expressed by the following chemical formula (I) of thepresent invention, R is an alkyl group having a carbon number of 25 to150. The ink composition for ink jet recording can achieve a highredispersion property by using a compound that includes R having acarbon number of not less than 25. The use of a compound expressed bythe following chemical formula (I) also is preferred for continuousejection stability, ejection performance after long-time non-operation,and long-time storage stability. In view of solubility in a water-basedink composition, a compound that includes R having a carbon number ofnot more than 150 is appropriate. The carbon number of R (alkyl group)is preferably 30 to 50, and more preferably 30 to 35. Further, n rangesfrom 2 to 100, preferably 10 to 50, and more preferably 20 to 50. Thealkyl group can be either linear or branched-chain, but a linear alkylgroup is preferred.

In view of solubility in water, HLB is not less than 4, preferably notless than 10, and more preferably ranges from 14 to 18.R—O—(CH₂CH₂O)_(n)—H  (I)

The compound expressed by the chemical formula (I) is used preferably inan amount of 0.1 to 8 wt %, more preferably 0.1 to 6 wt %, and even morepreferably 0.2 to 4 wt % with respect to the total weight of ink. Byadjusting the amount of the compound within the range of 0.1 to 8 wt %,the ink viscosity is not excessively high, so that the ink can providean intended effect.

Examples of the compound expressed by the chemical formula (I) includethe following products manufactured by Baker Petrolite Corporation inthe U.S.: “UNITHOX 420” (R is a linear alkyl group having a carbonnumber of 31 to 32, n is about 3, and HLB is 4); “UNITHOX 450” (R is alinear alkyl group having a carbon number of 31 to 32, n is about 10,and HLB is 10); “UNITHOX 480” (R is a linear alkyl group having a carbonnumber of 31 to 32, n is about 40, and HLB is 16); “UNITHOX 520” (R is alinear alkyl group having a carbon number of 38, n is about 3, and HLBis 4); “UNITHOX 550” (R is a linear alkyl group having a carbon numberof 38, n is about 12, and HLB is 10); “UNITHOX 720” (R is a linear alkylgroup having a carbon number of 48 to 49, n is about 4, and HLB is 4);and “UNITHOX 750” (R is a linear alkyl group having a carbon number of48 to 49, n is about 16, and HLB is 10).

The sublimation dye is preferably a disperse dye or solvent dye having asublimation property. These dyes can be used individually or as amixture, and the disperse dye is particularly preferred in view ofdispersibility and dyeing property.

Dyes that are sublimated or evaporated at 70 to 260° C. underatmospheric pressure, such as azo, anthraquinone, quinophthalone,styryl, diphenylmethane or triphenylmethane, oxazine, triazine,xanthene, methine, azomethine, acridine, and diazine are suitable forthe sublimation dye. Among these dyes, examples of a yellow disperse dyeinclude C. I. Disperse Yellow 51, 54, 60, 64, 65, 82, 98, 119, 160, and211. Examples of a red disperse dye include C. I. Disperse Red 4, 22,55, 59, 60, 146, 152, 191, 302, and Vat Red 41. Examples of a bluedisperse dye include C. I. Disperse Blue 14, 28, 56, 60, 72, 73, 77,334, 359, and 366. Other color components are, e.g., Violet 27 and 28.Examples of the solvent dye include C. I. Solvent Orange 25, 60, Red155, Blue 35, 36, 97, and 104.

To maintain the dispersion stability of the ink and to provide requiredprint concentration, the amount of the sublimation dye is preferably 0.2to 12 wt %, and more preferably 0.5 to 8 wt % with respect to the totalweight of ink.

The dispersant of the present invention not only disperses thesublimation dye into a water-based medium, but also has the function ofmaintaining the dispersion stability of the sublimation dye in the formof fine particles. There is no particular limitation to the dispersant,as long as it can be used with the sugar alcohol and the compoundexpressed by the chemical formula (I). For example, an anionicsurfactant, a nonionic surfactant, or a high-molecular surfactant can beused individually or as a mixture. The anionic surfactant and thenonionic surfactant are suitable for the dispersion of the disperse dyeor the solvent dye, and the anionic surfactant is particularlypreferred.

Examples of the anionic surfactant include naphthalene sulfonateformaldehyde condensate, lignin sulfonates, special arylsulfonateformaldehyde condensate (e.g., a formaldehyde condensate of sodium alkylnaphthalene sulfonate such as sodium butylnaphthalene sulfonate andsodium naphthalene sulfonate, a formaldehyde condensate of sodium cresolsulfonate and 2-Naphthol-6-sulfonic acid sodium salt, sodium cresolsulfonate formaldehyde condensate, or sodium creosote oil sulfonateformaldehyde condensate), and polyoxyethylene alkyl ether sulfate.

Examples of the nonionic surfactant include polyoxyethylene sorbitanfatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene acetylene glycol, polyoxyethylenederivatives, and oxyethylene oxypropylene block copolymers.

Examples of the high-molecular surfactant include polyacrylic partialalkyl ester, polyalkylene polyamine, polyacrylate, styrene-acrylic acidcopolymers, and vinylnaphthalene-maleic acid copolymers.

To maintain good dispersion stability of the sublimation dye, the amountof the dispersant is preferably 0.1 to 20 wt %, and more preferably 0.1to 12 wt % with respect to the total weight of ink.

In addition to the above materials, the ink of the present invention mayinclude various additives, if necessary, so as not to impede theattainment of the object of the present invention. Examples of theadditives include a surface control agent, a hydrotropic agent, a pHregulator, a viscosity modifier, a preservative, an antifungal agent, alight stabilizer, a chelating agent, and an antifoaming agent.

Examples of the surface control agent include a fluorochemicalsurfactant, a polyether modified dimethylpolysiloxane, and acrylicpolymers, and particularly the polyether modified dimethylpolysiloxaneand the acrylic polymers are suitable for the present invention. Thesesurface control agents are useful to control the surface tension of theink so that a material for forming the ink flow passage is wetted easilywhen it comes into contact with the ink. The amount of the surfacecontrol agent is preferably 0.05 to 1 wt %, and more preferably 0.1 to0.5 wt % with respect to the total weight of ink. When the amount isless than 0.05 wt %, the above effect is likely to be reduced. When theamount is more than 1 wt %, the above effect is not likely to beenhanced anymore.

A method for producing an ink for ink jet recording of the presentinvention is not particularly limited. For example, a preferred methodincludes the following:

(1) A sublimation dye, the sugar alcohol, a compound expressed by thechemical formula (I), a dispersant, and water are mixed and stirred toprepare predispersions. In this case, a water-soluble organic solvent orany of the above additives may be added as needed.

(2) The predispersions are placed in a wet mill (e.g., a sand mill) sothat the sublimation dye is pulverized into fine particles anddispersed, thereby producing dye dispersions.

(3) To the dye dispersions are added water or, if necessary, awater-soluble organic solvent and any of the above additives, and thenthe concentration is adjusted. The resultant liquid is filtered, e.g.,through a filter paper before use.

In this method, the sugar alcohol may be added either when thesublimation dye is pulverized or when the concentration is adjusted.Alternatively, the sugar alcohol may be divided and added in both cases.In view of workability, it is preferable to use an aqueous solution thatis prepared beforehand or a commercially available aqueous solution.

The compound expressed by the chemical formula (I) may be added eitherwhen the sublimation dye is pulverized or when the concentration isadjusted. Alternatively, the compound may be divided and added in bothcases. In view of workability, it is preferable to use an aqueoussolution of about 10 to 15 wt % that is prepared beforehand.

The average particle size of the sublimation dye obtained by the abovemethod is preferably not more than 0.5 μm, and more preferably rangesfrom 0.05 to 0.2 μm.

The foregoing explanation only gives some examples of a sublimation dye,sugar alcohol containing not less than four OH groups, a dispersant, andother components, and the present invention is not limited thereto.

A sublimation transfer dyeing method using the ink for sublimationtransfer ink jet recording of the present invention includes printingthe ink on a sheet medium by ink jet printing, and heating the sheetmedium to sublimate and transfer the sublimation dye onto an object tobe dyed.

The shape or material of the object to be dyed is not particularlylimited, as long as it can be dyed by sublimation transfer. In general,a cloth of hydrophobic fibers or sheet materials such as a resin filmand paper are used. However, not only the sheet materials but alsothree-dimensional, e.g., spherical or cubic materials can be used.

There is a method for sublimation transfer dyeing with the ink forsublimation transfer ink jet recording of the present invention, inwhich the ink is printed by ink jet printing on a sheet medium such aspaper, and this medium is then put on an object to be dyed such as ahydrophobic fiber product or resin film product for sublimationtransfer. There is also another method of the present invention, inwhich the ink is printed by ink jet printing on the film product thathas a releasable ink receptor layer and can be used for sublimation anddiffusion dyeing, the film product is then heated so that the lowerlayer is dyed by sublimation and diffusion, and the ink receptor layeris removed.

Examples of the sheet medium used in the former method include anon-coated recording sheet medium such as plain paper and a recordingsheet medium made of a sheet-like base with a coating layer thatincludes at least hydrophilic polymer and/or inorganic porous material.

The sheet medium used in the latter method corresponds to the releasableink receptor layer, and the object to be dyed corresponds to the lowerlayer of the film product.

In this case, the ink receptor layer is, e.g., a layer that mainlyincludes a water-soluble resin capable of quickly absorbing ink, and thewater-soluble resin component can be water-soluble or hydrophilicnatural or synthetic polymer. For example, the water-soluble resincomponent may include at least one selected from the following: apolyvinyl alcohol resin; a polyurethane resin; a polyvinyl acetal resin;polyvinyl methyl ether; vinyl methyl ether-maleic anhydride copolymers;polyvinyl pyrrolidone; vinyl pyrrolidone-styrene copolymers; vinylpyrrolidone-vinyl acetate copolymers; a water-soluble acrylic resinsynthesized from at least one monomer selected from acrylic acid,methacrylic acid, acrylic ester, and methacrylic acid or a mixture ofthe at least one monomer and other monomers; a vinyl resin such aspolyacrylamide; polyethylene oxide; a synthetic resin such aspolyglutamate; a semisynthetic resin of cellulose derivative such ascarboxymethyl cellulose or methylcellulose; and a natural resin such aschitin, chitosan, starch, or gelatin. Moreover, polyanionpolyelectrolyte such as alkali metal salt of polyacrylic acid orpolystyrene sulfonic acid, polycation polyelectrolyte such aspolyethyleneimine, polyvinylamine, polyallylamine, polyvinyl alkylammonium halide, or polyvinyl benzil alkyl ammonium halide, oramphoteric polyelectrolyte also can be used. Further, porous pigmentsuch as silica, clay, talc, diatomaceous earth, zeolite, calciumcarbonate, alumina, zinc oxide, or titanium oxide may be added in viewof the absorption of ink.

Examples of the lower layer of the film product, which is used as theobject to be dyed, include a polyester film, a polyurethane film, apolycarbonate film, a polyphenylene sulfide film, a polyimide film, anda polyamide-imide film, and a film obtained by coating the surface ofany one of these films with a resin that has no affinity for thesublimation dye (e.g., fluorocarbon resin), and further a film made of amaterial that is suitable for sublimation dyeing and neither melts norshrinks by heat during sublimation transfer.

The heating temperature for sublimation transfer depends on the type ofa sublimation dye to be used, and generally is about 150 to 200° C. Theheating time is about 2 to 10 minutes.

Hereinafter, the present invention will be described in more detail byway of examples. However, the present invention is not limited to thefollowing examples. In each of the examples, “parts” indicates “parts byweight” and “%” indicates “wt %” unless otherwise noted.

WORKING EXAMPLE 1

A mixture including 20 parts of red disperse dye dry cake (C. I.Disperse Red 60), 12 parts of special sodium arylsulfonate formaldehydecondensate (“DEMOL SN—B” manufactured by Kao Corporation) which is ananionic surfactant used as a dispersant, 5 parts of “UNITHOX 480”(manufactured by Baker Petrolite Corporation and corresponding to acompound expressed by the chemical formula (I) where R is a linear alkylgroup having a carbon number of 31 to 32, n is about 40, and HLB is 16),and 123 parts of water was prepared. This mixture was pulverized for 35hours in a sand mill using 330 parts of zircon beads with a diameter of0.4 mm, thus producing dispersions.

To the dispersions were added 5 parts of “UNITHOX 480”, 85 parts of“SORBITOL S” (manufactured by Nikken Chemicals Co., Ltd., D-sorbitolaqueous solution 70%), 2.0 parts of polyether modifieddimethylpolysiloxane (“BYK-348” manufactured by BYK-Chemie Japan) thatserves as a surface control agent, and water, so that ink with anadjusted dye concentration of 5% was obtained. The average particle sizeof the dye was 0.10 μm.

WORKING EXAMPLE 2

A mixture was prepared and pulverized in the same manner as in WorkingExample 1 except that 20 parts of yellow disperse dye dry cake (C. I.Disperse Yellow 54) were used instead of the red disperse dye dry cake,thus producing dispersions. To the dispersions were added 25 parts of“UNITHOX 480” that corresponds to a compound expressed by the chemicalformula (I), 215 parts of “SORBITOL S”, 2.5 parts of “BYK-348” thatserves as a surface control agent, and water, so that ink with anadjusted dye concentration of 2% was obtained. The average particle sizeof the dye was 0.12 μm.

WORKING EXAMPLE 3

A mixture including 20 parts of blue disperse dye dry cake (C. I.Disperse Blue 72), 12 parts of sodium β-naphthalene sulfonateformaldehyde condensate (“DEMOL N” manufactured by Kao Corporation)which is an anionic surfactant used as a dispersant, 5 parts of “UNITHOX480” that corresponds to a compound expressed by the chemical formula(I), and 123 parts of water was prepared. This mixture was pulverized inthe same manner as in Working Example 1 by using 330 parts of zirconbeads with a diameter of 0.4 mm, thus producing dispersions. To thedispersions were added 15 parts of “UNITHOX 480”, 130 parts of “SORBITOLS”, 2.4 parts of acrylic polymer (“BYK-381” manufactured by BYK-ChemieJapan) that serves as a surface control agent, and water, so that inkwith an adjusted dye concentration of 3.3% was obtained. The averageparticle size of the dye was 0.08 μm.

WORKING EXAMPLE 4

A mixture was prepared and pulverized in the same manner as in WorkingExample 1 to produce dispersions. To 40 parts of the dispersions wereadded 10 parts of “UNITHOX 480” that corresponds to a compound expressedby the chemical formula (I), 85 parts of “SORBITOL S”, 0.4 parts of“BYK-348” that serves as a surface control agent, and water, so that inkwith an adjusted dye concentration of 1.25% was obtained.

WORKING EXAMPLE 5

Ink was produced in the same manner as in Working Example 1 except that60 parts of xylitol was used instead of the “SORBITOL S” in WorkingExample 1.

WORKING EXAMPLE 6

Ink was produced in the same manner as in Working Example 1 except that60 parts of maltitol was used instead of the “SORBITOL S” in WorkingExample 1.

WORKING EXAMPLE 7

A mixture including 20 parts of red disperse dye dry cake (C. I.Disperse Red 60), 12 parts of special sodium arylsulfonate formaldehydecondensate (“DEMOL SN—B” manufactured by Kao Corporation) which is ananionic surfactant used as a dispersant, 3 parts of “UNITHOX 480”, and125 parts of water was prepared. This mixture was pulverized for 35hours in a sand mill using 330 parts of zircon beads with a diameter of0.4 mm, thus producing dispersions.

To the dispersions were added 85 parts of “SORBITOL S”, 2.0 parts of“BYK-348” that serves as a surface control agent, and water, so that inkwith an adjusted dye concentration of 5% was obtained. The averageparticle size of the dye was 0.10 μm.

WORKING EXAMPLE 8

A mixture was prepared and pulverized in the same manner as in WorkingExample 7 except that 20 parts of yellow disperse dye dry cake (C. I.Disperse Yellow 54) instead of the red disperse dye dry cake, 4 parts of“UNITHOX 480”, and 124 parts of water were used, thus producingdispersions. To the dispersion were added 215 parts of “SORBITOL S”, 2.5parts of “BYK-348” that serves as a surface control agent, and water, sothat ink with an adjusted dye concentration of 2% was obtained. Theaverage particle size of the dye was 0.12 μm.

WORKING EXAMPLE 9

A mixture was prepared and pulverized in the same manner as in WorkingExample 7 to produce dispersions. To 40 parts of the dispersions wereadded 3.3 parts of “UNITHOX 480” that corresponds to a compoundexpressed by the chemical formula (I), 85 parts of “SORBITOL S”, 0.4parts of “BYK-348” that serves as a surface control agent, and water, sothat ink with an adjusted dye concentration of 1.25% was obtained.

COMPARATIVE EXAMPLE 1

Ink was produced in the same manner as in Working Example 1 except that60 parts of glycerin was used instead of the “SORBITOL S” in WorkingExample 1.

COMPARATIVE EXAMPLE 2

Ink was produced in the same manner as in Working Example 1 except that60 parts of diethylene glycol was used instead of the “SORBITOL S” inWorking Example 1.

COMPARATIVE EXAMPLE 3

Ink was produced in the same manner as in Working Example 1 except thatspecial sodium arylsulfonate formaldehyde condensate (“DEMOL SN—B”manufactured by Kao Corporation) was used in equal amount instead of the“UNITHOX 480” in Working Example 1.

COMPARATIVE EXAMPLE 4

Ink was produced in the same manner as in Working Example 1 except that“UNITHOX 480” was used in equal amount instead of the “DEMOL SN—B” inWorking Example 1. The particle size of the dye was not less than 1 μm.When the ink thus produced was allowed to stand, the dye graduallyaggregated to form precipitates. Therefore, it was not possible to usethe ink for ink jet recording because the storage stability was poorwithout a dispersant.

Table 1 shows the ratio of components other than water for each of theink compositions in Working Examples 1 to 9 and Comparative Examples 1to 3.

Moreover, the following tests were conducted on each of the inksproduced in Working Examples 1 to 9 and Comparative Examples 1 to 3.Table 2 shows the results.

(1) Redispersion Property Test

A thin coating of ink composition (0.5 g) was applied to the surface ofa watch glass (φ90 mm), and the watch glass was placed in athermo-hygrostat that was kept at 30° C., 20% relative humidity and leftfor 3 hours. Then, the watch glass was taken out of the drier, and aperipheral portion of the dried ink was washed gently with a smallamount of water from the outside of the peripheral portion. The state ofthe ink was observed and evaluated as follows.

Evaluations: ∘ indicates that the ink is redispersed immediately withoutany aggregation; Δ indicates that aggregates in the form of a small thinfilm are partially generated, but not attached to the glass surface; andX indicates that a considerable amount of aggregates is generated andremain attached to the glass surface.

(2) Continuous Ejection Stability Test

Using a commercially available large-format ink jet plotter (“JV2-130”(piezo-type) manufactured by Mimaki Engineering, Co., Ltd), continuousprinting was performed under the conditions of 720×720 dpi resolution,single color, solid printing, and 1200 mm print width until some printerrors such as missing dots were caused.

Evaluations: ∘ indicates that no clogging occurs after 5 hours or more;Δ indicates that clogging occurs between 30 minutes and 1 hour; and Xindicates that clogging occurs within 30 minutes.

(3) Ejection Performance After Long-time Non-operation

The ink jet plotter continued to operate for 30 minutes under the aboveconditions, and then stopped for 48 hours. After normal cleaning, aprint test was conducted again to examine whether or not printing wasperformed normally under the same conditions.

Evaluations: ∘ indicates that normal printing can be performed byoperating one head cleaning in the manner specified for the ink jetplotter; Δ indicates that several cleaning cycles are necessary; and Xindicates that further cleaning cycles are not helpful in performingnormal printing.

(4) Sublimation Transfer Dyeing Test

A film product that has a releasable ink receptor layer and can be usedfor sublimation transfer dyeing was prepared in the following manner.First, a 50 μm thick polyester film substrate was coated with a 30 μmthick dye fixing layer made of polyurethane resin and was dried. Then,the dye fixing layer was coated with a 20 μm thick fluoroolefincopolymer resin layer and was cross-liked. After an adhesive layer andrelease paper were bonded to the back of the film, a cross-linkableurethane coating material for ink jet (“PATELACOL IJ-50”, a registeredtrademark of DAINIPPON INK AND CHEMICALS, INC.) was applied to thesurface of the film in a thickness of 20 μm so as to form an inkreceptor layer. Using the ink for sublimation transfer ink jet recordingproduced in Working Examples 1 to 9 and Comparative Examples 1 to 3, animage was printed on the ink receptor layer of the film product with thelarge-format ink jet plotter (“JV2-130” (piezo-type) manufactured byMimaki Engineering, Co., Ltd.), followed by heat treatment at about 170°C. for about 7 minutes in a hot-air dryer (“FINE OVEN DF62” manufacturedby Yamato Scientific Co., Ltd.). During the heat treatment, theconditions of heated steam issued from the vent of the dryer wereobserved. Upon removal of the ink receptor layer, the image was formedinto the film product by sublimation and diffusion dyeing.

Evaluations: ∘ indicates that no smoky steam is generated; Δ indicatesthat a small amount of smoky steam is generated; X indicates that aconsiderable amount of smoky steam is generated. TABLE 1 Inkcompositions in Working Examples and Comparative Examples (wt %)Comparative Working Examples Examples 1 2 3 4 5 6 7 8 9 1 2 3 Y-54 — 2.0— — — — — 2.0 — — — — R-60 5.0 — — 1.25 5.0 5.0 5.0 — 1.25 5.0 5.0 5.0B-72 — — 3.3 — — — — — — — — — DEMOL SN-B 3.0 1.2 — 0.75 3.0 3.0 3.0 1.20.75 3.0 3.0 5.5 DEMOL N — — 2.0 — — — — — — — — — UNITHOX 480 2.5 3.03.5 2.8 2.5 2.5 0.75 0.4 1.0 2.5 2.5 — SORBITOL S 15 15 15 15 — — 15 1515 — — 15 Xylitol — — — — 15 — — — — — — — Maltitol — — — — — 15 — — — —— — Glycerin — — — — — — — — — 15 — — Diethylene G — — — — — — — — — —15 — BYK-348 0.50 0.25 — 0.10 0.50 0.50 0.50 0.25 0.10 0.50 0.50 0.50BYK-381 — — 0.40 — — — — — — — — —“Y-54” represents yellow disperse dye dry cake (C. I. Disperse Yellow54), “R-60” represents red disperse dye dry cake (C. I. Disperse Red60), “B-72” represents blue disperse dye dry cake (C. I. Disperse Blue72), and “Diethylene G” represents diethylene glycol. The ratio of“SORBITOL S” is expressed in terms of solid content.

TABLE 2 Comparative Working Examples Examples 1 2 3 4 5 6 7 8 9 1 2 3Redispersion ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ X property Continuous ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ Δ ejection stability Ejection ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ X performanceafter long-time non-operation Conditions dur- ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ X X ◯ing sublimation transfer

As can be seen from the results, Working Examples 1 to 9 do not causeany smoky steam during heat treatment and also are superior inredispersion property, continuous ejection stability, and ejectionperformance after long-time non-operation. Comparative Examples 1 and 2,in which D-sorbitol is replaced by glycerin or diethylene glycol, causeconsiderable smoky steam. Comparative Example 3, in which an anionicdispersant is used instead of the compound expressed by the chemicalformula (I), does not cause smoky steam, but is inferior in redispersionproperty, continuous ejection stability, and ejection performance afterlong-time non-operation.

Industrial Applicability

An ink for ink jet recording of the present invention that uses asublimation dye as a color component has the effects of not onlymaintaining required performances such as storage stability andhigh-quality recording images, but also achieving a high redispersionproperty with reduced environmental pollution, effectively preventingnozzle clogging, and ensuring stable ejection by normal cleaning bothduring long continuous operation and after stopping the operation of anapparatus for a long time. Thus, the ink of the present invention issuitable for an ink for ink jet recording that uses a sublimation dye asa color component.

A sublimation transfer dyeing method of the present invention allows theink for sublimation transfer ink jet recording to be printed by ink jetprinting, followed by sublimation transfer. Thus, this method can reduceenvironmental pollution while maintaining required performances such asstorage stability and high-quality recording images of the ink used fordyeing. Therefore, the ink used can improve the redispersion propertyand effectively prevent nozzle clogging, which makes it possible toperform dyeing all the time and to ensure stable ejection by normalcleaning both during long continuous operation and after stopping theoperation of an apparatus for a long time. Thus, the method of thepresent invention is suitable for ink jet printing that uses ink forsublimation transfer ink jet recording.

1. An ink for sublimation transfer ink jet recording comprising: water;at least one sugar alcohol containing not less than four OH groups; asublimation dye; a dispersant; and a compound expressed by the followingchemical formula (I):R—O—(CH₂CH₂O)_(n)—H  (I) where r is an alkyl group having a carbonnumber of 25 to 150 and n is from 2 to
 100. 2. The ink for sublimationtransfer ink jet recording according to claim 1, wherein the sugaralcohol containing not less than four OH groups is at least one selectedfrom the group consisting of D-sorbitol, xylitol, and maltitol.
 3. Theink for sublimation transfer ink jet recording according to claim 1,wherein R is an alkyl group having a carbon number of 30 to 50 and n isfrom 10 to 50 in the chemical formula (I).
 4. The ink for sublimationtransfer ink jet recording according to claim 1, whereinhydrophile-lipophile balance (HLB) of the compound expressed by thechemical formula (I) is not less than
 10. 5. The ink for sublimationtransfer ink jet recording according to claim 1, wherein the sublimationdye is at least one selected from the group consisting of a disperse dyeand a solvent dye.
 6. The ink for sublimation transfer ink jet recordingaccording to claim 1, wherein the dispersant is at least one selectedfrom the group consisting of an anionic surfactant, a nonionicsurfactant, and a high-molecular surfactant.
 7. The ink for sublimationtransfer ink jet recording according to claim 1, wherein an amount ofthe sugar alcohol containing not less than four OH groups is 0.5 to 50wt % with respect to a total weight of ink.
 8. The ink for sublimationtransfer ink jet recording according to claim 1, wherein an amount ofthe sugar alcohol containing not less than four OH groups is 0.5 to 50wt %, an amount of the sublimation dye is 0.2 to 12 wt %, an amount ofthe dispersant is 0.1 to 20 wt %, and an amount of the compoundexpressed by the chemical formula (I) is 0.1 to 8 wt % with respect to atotal weight of ink.
 9. The ink for sublimation transfer ink jetrecording according to claim 1, wherein the ink does not substantiallyinclude a water-soluble organic solvent.
 10. A sublimation transferdyeing method comprising: printing the ink for sublimation transfer inkjet recording according to any one of claims 1 to 9 on a sheet medium byink jet printing; and heating the sheet medium to sublimate and transferthe sublimation dye onto an object to be dyed.